In his Sunday Angelus address Pope Francis commended world leaders for reaching an agreement in the recently-concluded Paris climate talks, urging the international community promptly put it into action.

"The conference on climate has just concluded in Paris with the adoption of an agreement, defined by many as historic," the Pope said Dec. 13.

Implementing the plan, he said, will require "a concerted and generous commitment on the part of each one," and expressed his hope that the agreement will give special attention to the most vulnerable.

The Vatican's Secretary of State Cardinal Pietro Parolin was one of leaders representing 150 nations present for the Nov. 30-Dec. 11 discussions of the COP-21 summit on climate change in Paris, aimed at finding legally binding reductions in greenhouse gas emissions and holding global average temperatures under a two degrees Celsius increase over preindustrial global temperatures.

The new deal holds that global greenhouse gas emissions will be cut by half of what is needed to prevent an increase in atmospheric temperatures of two degrees Celsius, according to the New York Times.

The agreement also requires that every country participate, putting forward their own plan to cut carbon emissions through 2025-2030. Countries will also be legally required to meet every five years beginning in 2023 in order to publicly report on their progress compared to their plans.

In his comments, Pope Francis exhorted the entire international community "to promptly continue the path taken, as a sign of solidarity which becomes ever more active."

Francis led pilgrims gathered in St. Peter's Square in the traditional Marian prayer after returning from the Roman basilica of St. John Lateran, where he celebrated Mass and opened the basilica's Holy Door for the Jubilee of Mercy.

In his speech ahead of the prayer, the Pope identified three different groups who spoke to John the Baptist in the day's Gospel from Luke, asking him "what must we do?" in order to repent and prepare for the Lord.

These groups are the general crowd, the tax collectors and the soldiers, Francis said, noting that in his response to each of them, John indicates that the heart of conversion is love of one's neighbor, which is shown through concrete acts justice and solidarity, the Pope said.

In asking the crowd to share with those in need, the tax collectors not to demand more than the due amount, and in telling the soldiers not to extort but to be happy with their pay, John the Baptist shows us what the temptations were of those who had power at the time, Francis said.

"Things haven't changed much, eh?" he observed, noting that despite these tendencies "no category of person is excluded from walking the path of conversion in order to obtain salvation."

"God doesn't prevent anyone from the possibility of salvation," including the tax collectors, who were considered sinners "by definition" at the time.

Instead, Francis said that God "is anxious to use mercy toward all and to welcome each person in the tender embrace of reconciliation and forgiveness."

John's instructions also go for us today, he said, noting that justice, solidarity and sobriety are essential values on the path of conversion.

A specific dynamic of this repentance and conversion is "joy," he said, adding that joy is an important aspect of conversion, since "whoever converts and becomes close to the Lord feels joy."

In a world with many problems, it takes courage and faith to talk about joy, he said, adding that our joy as Christians "comes from the certainty that the Lord is close. He is close with his mercy, tenderness, love and forgiveness."

Pope Francis concluded his address by praying that Mary would intercede in helping us to be strengthened in faith, "so that we know how to welcome the God of joy, who always desires to live in the midst of his children."

As our mother, he said, Mary teaches us "to share the tears of those who cry, (in order to) be able to also share their smiles."